This invention relates to an improved piston-connecting rod unit. Such a unit is known to comprise a piston provided with a transverse seat in its side wall for a gudgeon pin which is fitted to the small end of a connecting rod usually in a floating manner, ie such as to allow the connecting rod small end to rotate freely relative to the piston.
Because of the high specific pressure exerted by the piston on the gudgeon pin and by the gudgeon pin on the cooncting rod, this type of connection requires either a very long gudgeon pin or, if this length has to be limited, a gudgeon pin of increased diameter with consequent increase in the alternating masses. Furthermore, when the gudgeon pin is of the floating type it is locked axially by two spring circlips, the presence of which however reduces the gudgeon pin bearing surfaces. On the other hand, if the gudgeon pin is forced into the connecting rod so that it is no longer floating, the result is permanent flexural deformation and ovalisation of the gudgeon pin, which can lead to piston fracture or seizing.